The present invention relates to a ceramic heater, for example a ceramic heater to be used in a glow plug for a diesel engine.
Recently, a ceramic heater provided with a heat generator made of a conductive ceramic sintered body, has been proposed. However, this ceramic heater has a problem that minute cracks are produced in the heat generator while being used under such a condition as being exposed to low temperature liquid such as water and oil.
The ceramic heater can be used as a heater of a diesel engine because the heat generator is of a simple construction and has excellent quick heating property. In this case, the heat generator generates heat of about 1300.degree. C. When the high temperature heat generator is exposed to light oil as a fuel, minute cracks are produced in the heat generator so as to increase the resistance thereof.